In medical technology, but in other areas as well, such as in laboratories, it is often necessary to transfer liquids from one container into another in a specific sequence, and then to transport them further after a certain period of time or after a predetermined interval, for example a mixing or a chemical reaction.
Dialysis according to the hemofiltration procedure can be mentioned as one example. In this procedure, a bicarbonate-electrolyte solution is used as the medium. Since the two individual solutions, i.e., the bicarbonate solution and the electrolyte solution, can only be kept in a mixed state for 24 hours, they are stored in separate bags and not mixed until just before their application. Since transfer to the patient of only one of the two components can be critical, provisions have to be made to ensure that in every instance, before connection to a transfusion set, the two solutions are mixed together and that an inadvertent connection of just one of the solution components is avoided through effective precautions.
In the area of application mentioned above, it is known that the two solutions are to be stored separately from each other in two separate bags, and only mixed together immediately before use. This system does not, however, exclude the possibility that as a result of inattentive operation, the combining and mixing is neglected, and only one of the components is dispensed into the transfusion set.
A system of that type has become known, for example, from DE-36 27 231 A1, in which is described a so-called transfer device for the mixing of medicines located in two different containers. However, this system still retains exactly that disadvantage described above. Indeed, there is in this reference a description of a temporal sequence for effecting the connection between the two containers. However, this is not against the background that this connection must be carried out in an absolutely essential temporal sequence.
In addition, it is known that both solutions can be stored separated by a wall in a double-chamber bag. When this is done, the permissible storage period is determined by the component that can be kept for the shorter period, so that if the expiration date has passed, the other component, which by itself would still be usable, is lost as well. Furthermore, with a double-chamber bag, two liquids are always allocated to each other in specific quantity and concentration, so that in storage the appropriate pairing for each combination must be retained.